DOCSLIB.ORG

The San Andreas Fault in the San Francisco Bay Area, California: a Geology Fieldtrip Guidebook to Selected Stops on Public Lands

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
The San Andreas Fault in the San Francisco Bay Area, California: a Geology Fieldtrip Guidebook to Selected Stops on Public Lands The San Andreas Fault In The San Francisco Bay Area, California: A Geology Fieldtrip Guidebook To Selected Stops On Public Lands By Philip W. Stoffer U.S. Geological Survey Open-File Report 2005-1127 2005 U.S. Department of Interior U.S. Geological Survey ABSTRACT: This guidebook contains a series of geology fieldtrips with selected destinations along the San Andreas Fault in part of the region that experienced surface rupture during the Great San Francisco Earthquake of 1906. Introductory materials present general information about the San Andreas Fault System, landscape features, and ecological factors associated with faults in the South Bay, Santa Cruz Mountains, the San Francisco Peninsula, and the Point Reyes National Seashore regions. Trip stops include roadside areas and recommended hikes along regional faults and to nearby geologic and landscape features that provide opportunities to make casual observations about the geologic history and landscape evolution. Destinations include the sites along the San Andreas and Calaveras faults in the San Juan Bautista and Hollister region. Stops on public land along the San Andreas Fault in the Santa Cruz Mountains in Santa Clara and Santa Cruz counties include in the Loma Prieta summit area, Forest of Nicene Marks State Park, Lexington County Park, Sanborn County Park, Castle Rock State Park, and the Mid Peninsula Open Space Preserve. Destinations on the San Francisco Peninsula and along the coast in San Mateo County include the Crystal Springs Reservoir area, Mussel Rock Park, and parts of Golden Gate National Recreation Area, with additional stops associated with the San Gregorio Fault system at Montara State Beach, the James F. Fitzgerald Preserve, and at Half Moon Bay. Field trip destinations in the Point Reyes National Seashore and vicinity provide information about geology and character of the San Andreas Fault system north of San Francisco. Notes about cover map image: Small dots within colored areas show the location of stops discussed in chapter field guides. Abbreviations for locations include San Francisco (SF), San Jose (SJ), Hollister (H), San Juan Bautista (SJB), Half Moon Bay (HMB), Pacifica (P), and Santa Cruz (SC). The orange line represents the San Andreas Fault (SAF) section that ruptured in the Great San Francisco Earthquake of 1906. Special thanks to SEPM (Society of Sedimentary Geology)! Parts of this field trip were previewed on the Pacific Section SEPM Fall Field Trip, October 9-10, 2004. The society hosts field trips annually. Special thanks are extended to the society and its leaders for organizing and supporting these outdoor education experiences! ii TABLE OF CONTENTS Introduction ………………………………………………………………………………………. 1 San Andreas Fault: An Overview ………………………………………………………… 1 Bay Area Faults and Earthquakes ………………………………………………………… 4 Comparison of the Bay Area earthquakes: 1906 and 1989 ………………………………. 5 Comparison of Earthquake Magnitude and Intensity Scales ..……………………………. 7 Geologic Features of the San Andreas Fault ……………………………………………… 8 A Geologic Time Scale …………………………………………………………………… 11 Types of Faults …………………………………………………………………………… 12 Geomorphic Features Observable Along Faults …………………….…………………. 13 Geomorphic Features Associated With Landslides ………………………………………. 16 Plant Communities of the San Francisco Bay Region ……………………………………. 18 Field Trip to the Calaveras and San Andreas Faults: Hollister and San Juan Bautista Region ….. 23 Field Trip to Lexington Reservoir and Loma Prieta Peak Areas ………………………………… 37 Forest of Nisene Marks State Park: Epicenter of the 1989 Loma Prieta Earthquake ……………. 51 Lyndon Canyon and Ranch Lake Trail, Sanborn County Park ………………………………….. 53 Earthquake Trail, Sanborn County Park …………………………………………………............ 55 Field Trip to the Skyline Ridge Region in the Santa Cruz Mountains ………………………….. 68 The San Andreas and San Gregorio Fault Systems in San Mateo County……………………… 81 Geology at Point Reyes National Seashore and Vicinity……….………………..……………… 102 iii Introduction This volume is a general geology field guide to the San Andreas Fault in the San Francisco Bay Area. The first section provides a brief overview of the San Andreas Fault in context to regional California geology, the Bay Area, and earthquake history with emphasis of the section of the fault that ruptured in the Great San Francisco Earthquake of 1906. This first section also contains information useful for discussion and making field observations associated with fault- related landforms, landslides and mass-wasting features, and the plant ecology in the study region. The second section contains field trips and recommended hikes on public lands in the Santa Cruz Mountains, along the San Mateo Coast, and at Point Reyes National Seashore. These trips provide access to the San Andreas Fault and associated faults, and to significant rock exposures and landforms in the vicinity. Note that more stops are provided in each of the sections than might be possible to visit in a day. The extra material is intended to provide optional choices to visit in a region with a wealth of natural resources, and to support discussions and provide information about additional field exploration in the Santa Cruz Mountains region. An early version of the guidebook was used in conjunction with the Pacific SEPM 2004 Fall Field Trip. Selected references provide a more technical and exhaustive overview of the fault system and geology in this field area; for instance, see USGS Professional Paper 1550-E (Wells, 2004). San Andreas Fault: An Overview The catastrophe caused by the 1906 earthquake in the San Francisco region started the study of earthquakes and California geology in earnest. Three days after the earthquake, Andrew C. Lawson, the chairman of the geology department of University of California, Berkeley, organized (and was appointed head of by the governor) a State Earthquake Investigation Commission. In 1908 the "Lawson Report" was released. This massive volume contains detailed engineering studies of urban damage caused by the earthquake and fire, and includes studies of the surface rupture and ground failure along the San Andreas Fault and throughout the region. The Lawson Report is still regarded as a significant scientific resource and is hailed as the first organized effort to study earthquake hazards and fault geology in America. In the century that followed, several thousand technical reports and articles have been written about the San Andreas Fault System alone, and this body of knowledge was a fundamental part of the development of the theory of plate tectonics. A Right-Lateral Strike-Slip Fault Motion A major question raised by the 1906 earthquake investigations was why did the surface rupture along the San Andreas Fault show mostly horizontal offset? Although the surface rupture along the fault was highly variable, it was obvious that the west side of the fault had moved northward relative to the east side as much as 20 feet near Point Reyes. This right-lateral offset observed in the 1906 earthquake was not typical of previously studied earthquake surface ruptures, and was contradictory to existing theories of earth processes responsible for the evolution of the landscape. Studies of the San Andreas Fault and California geology have since demonstrated that some great blocks of rock have indeed moved laterally long distances over geologic time. Landscape features such as streams as well as geologically similar bedrock blocks (including distinct volcanic and plutonic rocks, and unique sedimentary deposits of all ages) are all offset along the fault, with youngest rocks offset less than older rocks. The amount and rate of offset along the fault is not consistent from place to place, partly because at the surface the San Andreas often consists of a complex system of parallel and interconnecting faults. Some sections of the fault are constantly creeping along, whereas other sections are locked during periods between episodic large earthquakes. In general, the western Pacific Plate is moving northward at about two inches per year relative to the North American Plate, and much of this motion is accommodated along the San Andreas Fault and is responsible for many large magnitude earthquakes (see figs 1-1 and 1-2). However, the physical offset of the brittle crust near the earth's surface occurs along a number of known and unknown faults, often in an unpredictable fashion. In addition, movement along the San Andreas Fault is not purely right-lateral. There is a component attributed to compressional forces developed across the fault trace as the two plates grind against each other. This compression helped produce the coastal mountain ranges along the fault system through California. The ratio of compression to horizontal displacement typically ranges from 1:10 to 1:20 but varies considerably from one section or strand of the fault to another. 1 Figure 1-1. The San Andreas Fault System has gradually evolved since middle Tertiary time (beginning ~28 million years ago). The San Andreas Fault System grew as a remnant of a oceanic crustal plate and a spreading ridge (like the Juan de Fuca Ridge) were subducted beneath the North American Plate as it moved west relative to the Pacific Plate. The result was the development of a crustal fracture zone with right-lateral offset that propagated along the continental margin (see fig. 1-3 below). This action also slivered off pieces of the North American Plate and added them to the Pacific Plate. Although estimates vary, the maximum offset along the
Load more

Recommended publications
  • Introduction San Andreas Fault: an Overview
    Introduction This volume is a general geology field guide to the San Andreas Fault in the San Francisco Bay Area. The first section provides a brief overview of the San Andreas Fault in context to regional California geology, the Bay Area, and earthquake history with emphasis of the section of the fault that ruptured in the Great San Francisco Earthquake of 1906. This first section also contains information useful for discussion and making field observations associated with fault- related landforms, landslides and mass-wasting features, and the plant ecology in the study region. The second section contains field trips and recommended hikes on public lands in the Santa Cruz Mountains, along the San Mateo Coast, and at Point Reyes National Seashore. These trips provide access to the San Andreas Fault and associated faults, and to significant rock exposures and landforms in the vicinity. Note that more stops are provided in each of the sections than might be possible to visit in a day. The extra material is intended to provide optional choices to visit in a region with a wealth of natural resources, and to support discussions and provide information about additional field exploration in the Santa Cruz Mountains region. An early version of the guidebook was used in conjunction with the Pacific SEPM 2004 Fall Field Trip. Selected references provide a more technical and exhaustive overview of the fault system and geology in this field area; for instance, see USGS Professional Paper 1550-E (Wells, 2004). San Andreas Fault: An Overview The catastrophe caused by the 1906 earthquake in the San Francisco region started the study of earthquakes and California geology in earnest.
    [Show full text]
  • 2016 Hayward Local Hazard Mitigation Plan
    EARTHQUAKE SEA LEVEL RISE FLOOD DROUGHT CLIMATE CHANGE LANDSLIDE HAZARDOUS WILDFIRE TSUNAMI MATERIALS LOCAL HAZARD MITIGATION PLAN 2 016 CITY OF heart of the bay TABLE OF CONTENTS TABLE OF FIGURES ......................................................................................................................... 4 TABLE OF TABLES .......................................................................................................................... 4 EXECUTIVE SUMMARY 5 RISK ASSESSMENT & ASSET EXPOSURE ......................................................................................... 6 EARTHQUAKE ................................................................................................................................. 6 FIRE ............................................................................................................................................... 6 LANDSLIDE ..................................................................................................................................... 6 FLOOD, TSUNAMI, AND SEA LEVEL RISE .......................................................................................... 6 DROUGHT ....................................................................................................................................... 6 HAZARDOUS MATERIALS ................................................................................................................. 7 MITIGATION STRATEGIES ...............................................................................................................
    [Show full text]
  • Beach Report Card Program Is Funded by Grants From
    2013-2014 Annual 2013–2014 Heal the Bay is a nonprofit environmental organization making Southern California coastal waters and watersheds, including Santa Monica Bay, safe, healthy and clean. We use science, education, community action and advocacy to pursue our mission. The Beach Report Card program is funded by grants from Swain Barber Foundation ©2014 Heal the Bay. All Rights Reserved. The fishbones logo is a trademark of Heal the Bay. The Beach Report Card is a service mark of Heal the Bay. We at Heal the Bay believe the public has the right to know the water quality at their favorite beaches. We are proud to provide West Coast residents and visitors with this information in an easy-to-understand format. We hope beachgoers will use this information to make the decisions necessary to protect their health. This page: Avalon Bay, Catalina Island Cover photo: The Wedge, Newport Beach TABLE OF CONTENTS SECTION ONE Introduction Executive Summary 6 SECTION TWO The Beach Report Card County by County Summary Reports 16 SECTION THREE BRC Impacts and News California Beach Types and Water Quality 48 The Clean Beach Initiative (CBI) 50 Total Maximum Daily Loads (TMDLs) 53 Major Beach News 55 Recommendations for the Coming Year 65 Frequently Asked Questions (FAQs) 70 SECTION FOUR Appendices Methodology for California 76 Methodology for Oregon and Washington 78 2013-2014 Honor Roll 80 Grades by County – California 81 Grades by County – Washington 94 Grades by County – Oregon 97 Index and Glossary 98 Acknowledgements 100 5 Executive Summary Beaches in the U.S. accommodate nearly two billion beach visits each year1 and provide enormous economic benefits to their communities.
    [Show full text]
  • Considerations for Rezoning on Lakes
    STATE OF MAINE DEPARTMENT OF AGRICULTURE, CONSERVATION & FORESTRY LAND USE PLANNING COMMISSION 22 STATE HOUSE STATION WALTER E. WHITCOMB PAUL R. LEPAGE AUGUSTA, MAINE 04333-0022 COMMISSIONER GOVERNOR NICHOLAS D. LIVESAY EXECUTIVE DIRECTOR Memorandum To: LUPC Commissioners From: Samantha Horn, Planning Manager Ben Godsoe, Senior Planner Date: October 5, 2018 Re: Considerations for Rezoning Near Lakes, Staff Analysis Lake resources are important to Maine’s character, environment and economy. Healthy lakes are a strong draw for local residents and visitors alike, and play a critical role in sustaining fish and wildlife populations. When the Commission considers the location of future subdivisions, it is important to be deliberate about which lakes may be near new zones for subdivisions. The May 2018 draft of rule revisions for adjacency included a proposal that any new zones for waterfront subdivision should be either 1) on a lake or pond that is within a certain distance of services (i.e., within primary or secondary locations); or 2) on a lake or pond that is already developed. Outside of primary or secondary locations, lakes under the proposed revisions that could be eligible for rezoning include management class 3, 4, and 5 lakes, as well as certain class 7 lakes. During the public hearing on the draft rule revisions, commenters raised concerns that there was not sufficient information available to tell which or how many class 7 lakes qualify as having sufficient development to make them potentially be eligible for rezoning. Without this information, commenters raised concerns that a large number of lakes could possibly be “open for development.” Commenters requested more information on which class 7 lakes could be affected by the proposal.
    [Show full text]
  • Why Did the Southern Gulf of California Rupture So Rapidly?—Oblique Divergence Across Hot, Weak Lithosphere Along a Tectonically Active Margin
    Why did the Southern Gulf of California rupture so rapidly?—Oblique divergence across hot, weak lithosphere along a tectonically active margin breakup, is mainly dependent on the thermal structure, crust- Paul J. Umhoefer, Geology Program, School of Earth Sciences & Environmental Sustainability, Northern Arizona University, al thickness, and crustal strength of the lithosphere when Flagstaff, Arizona 86011, USA; [email protected] rifting begins (e.g., Buck, 2007), as well as forces at the base of the lithosphere and far-field plate interactions (Ziegler and Cloetingh, 2004). ABSTRACT Continental rupture at its two extremes creates either large Rifts in the interior of continents that evolve to form large ocean basins or small and narrow marginal seas depending oceans typically last for 30 to 80 m.y. and longer before com- largely on the tectonic setting of the rift. Rupture of a conti- plete rupture of the continent and onset of sea-floor spreading. nent that creates large oceans most commonly initiates as A distinct style of rifts form along the active tectonic margins of rifts in old, cold continental lithosphere or within former continents, and these rifts more commonly form marginal seas large collisional belts in the interior of large continents, part and terranes or continental blocks or slivers that are ruptured of the process known as the Wilson Cycle (Wilson, 1966). away from their home continent. The Gulf of California and the Rupture to create narrow marginal seas commonly occurs in Baja California microplate make up one of the best examples active continental margins and results in the formation of of the latter setting and processes.
    [Show full text]
  • Patricia Persaud
    A bottom-driven mechanism for distributed faulting in the Gulf of California Rift Patricia Persaud1, Eh Tan2, Juan Contreras3 and Luc Lavier4 2017 GeoPRISMS Theoretical and Experimental Institute on Rift Initiation and Evolution [email protected], Department of Geology and Geophysics, Louisiana State University, Baton Rouge, Louisiana 70803; 2 Institute of Earth Sciences, Academia Sinica, Taipei, Taiwan; 3 Centro de Investigación Científca y de Educación Superior de Ensenada, Ensenada, BC, Mexico; 4 University of Texas Austin, Institute for Geophysics, Austin, TX 78712 Introduction Modeling strain partitioning and distribution of deformation in Application to the Northern Gulf Observations in the continent-ocean transition of the Gulf • Our model with an obliquity of 0.7, and linear basal velocity of California (GOC) show multiple oblique-slip faults oblique rifts boundary conditions reveals a delocalized fault pattern of distributed in a 200x70 km2 area (Fig. 4). In contrast, north contemporaneously active faults, multiple rift basins and and south of this broad pull-apart structure, major transform variable fault dips representative of faulting in the N. Gulf. faults accommodate plate motion. We propose that the FIG. 9 • The r=0.7 model is able to predict the broad geometrical mechanism for distributed faulting results from the boundary arrangement of the two Upper Delfn, Lower Delfn and conditions present in the GOC, where basal shear is Wagner basins as segmented basins with tilted fault blocks, distributed between the southernmost fault of the San and multiple oblique-slip bounding faults characteristic of Andreas system and the Ballenas Transform fault. FIG. 8 incomplete strain-partitioning. We also confrm with our We hypothesize that in oblique-extensional settings numerical results that numerous oblique-slip faults whether deformation is partitioned in a few dip-slip and accommodate slip in the study area instead of throughgoing strike-slip faults, or in numerous oblique-slip faults may large-offset transform faults.
    [Show full text]
  • 1968 General Plan
    I I I I I I MONTEREY COUNTY GENERAL PLAN I MONTEREY COUNTY, STATE OF CALIFORNIA I I I I ADOPTED BY THE MONTEREY COUNTY PLANNING COMMISSION JULY 10, 1968 I ADOPTED BY THE BOARD OF SUPERVISORS OF MONTEREY COUNTY OCTOBER 22, 1968 I I I I I I I I I I I I I I I I I I 0 N I I I MONTEREY COUNTY I I I I I I PREFACE I The Monterey County General Plan is an attempt to establish a county philosophy based on the values and desires of the people. This in turn becomes a valid basis for decisions by public bodies as well as private enterprise. Such a pro­ cedure is vitally needed in our rapidly changing environment. The General Plan I is a study of the ever changing pattern of Monterey County --a mirror in which to review the past, to comprehend the present, and to contemplate the future, This plan reflects years of research and study as well as many other reports such as I the continuing Facts and Figures, Recreation in Monterey County, Beach Acqui­ sition, and other plans which are shown as separate documents h~cause of the volume of material. I The size of Monterey County, its variety of climate, vegetation, and land forms make it imperative that only large land uses or broad proposals be used to portray geographically the objectives desired for the future development of the County. I Accordingly, in addition to the maps, greater emphasis in the General Plan is placed on the text which conveys in words the objectives as well as the princi­ ples and standards recommended to make them effective.
    [Show full text]
  • 2020 Pacific Coast Winter Window Survey Results
    2020 Winter Window Survey for Snowy Plovers on U.S. Pacific Coast with 2013-2020 Results for Comparison. Note: blanks indicate no survey was conducted. REGION SITE OWNER 2017 2018 2019 2020 2020 Date Primary Observer(s) Gray's Harbor Copalis Spit State Parks 0 0 0 0 28-Jan C. Sundstrum Conner Creek State Parks 0 0 0 0 28-Jan C. Sundstrum, W. Michaelis Damon Point WDNR 0 0 0 0 30-Jan C. Sundstrum Oyhut Spit WDNR 0 0 0 0 30-Jan C. Sundstrum Ocean Shores to Ocean City 4 10 0 9 28-Jan C. Sundstrum, W. Michaelis County Total 4 10 0 9 Pacific Midway Beach Private, State Parks 22 28 58 66 27-Jan C. Sundstrum, W. Michaelis Graveyard Spit Shoalwater Indian Tribe 0 0 0 0 30-Jan C. Sundstrum, R. Ashley Leadbetter Point NWR USFWS, State Parks 34 3 15 0 11-Feb W. Ritchie South Long Beach Private 6 0 7 0 10-Feb W. Ritchie Benson Beach State Parks 0 0 0 0 20-Jan W. Ritchie County Total 62 31 80 66 Washington Total 66 41 80 75 Clatsop Fort Stevens State Park (Clatsop Spit) ACOE, OPRD 10 19 21 20-Jan T. Pyle, D. Osis DeLaura Beach OPRD No survey Camp Rilea DOD 0 0 0 No survey Sunset Beach OPRD 0 No survey Del Rio Beach OPRD 0 No survey Necanicum Spit OPRD 0 0 0 20-Jan J. Everett, S. Everett Gearhart Beach OPRD 0 No survey Columbia R-Necanicum R. OPRD No survey County Total 0 10 19 21 Tillamook Nehalem Spit OPRD 0 17 26 19-Jan D.
    [Show full text]
  • Discover California State Parks in the Monterey Area
    Crashing waves, redwoods and historic sites Discover California State Parks in the Monterey Area Some of the most beautiful sights in California can be found in Monterey area California State Parks. Rocky cliffs, crashing waves, redwood trees, and historic sites are within an easy drive of each other. "When you look at the diversity of state parks within the Monterey District area, you begin to realize that there is something for everyone - recreational activities, scenic beauty, natural and cultural history sites, and educational programs,” said Dave Schaechtele, State Parks Monterey District Public Information Officer. “There are great places to have fun with families and friends, and peaceful and inspirational settings that are sure to bring out the poet, writer, photographer, or artist in you. Some people return to their favorite state parks, year-after-year, while others venture out and discover some new and wonderful places that are then added to their 'favorites' list." State Parks in the area include: Limekiln State Park, 54 miles south of Carmel off Highway One and two miles south of the town of Lucia, features vistas of the Big Sur coast, redwoods, and the remains of historic limekilns. The Rockland Lime and Lumber Company built these rock and steel furnaces in 1887 to cook the limestone mined from the canyon walls. The 711-acre park allows visitors an opportunity to enjoy the atmosphere of Big Sur’s southern coast. The park has the only safe access to the shoreline along this section of cast. For reservations at the park’s 36 campsites, call ReserveAmerica at (800) 444- PARK (7275).
    [Show full text]
  • South Fork Coquille Watershed Analysis
    DOCUMENT A 13.66/2: COQUILLE fiVE, LOWER S.F. 17 10 03 00* I C 66x 1 COQUILLE RIVER, UPPER S.F 17 1:-03 01* ' United States Q, '0) Departimnt of Agriculture THIS PUBLICATION Forest Serilce CMN FE CHECKED OUT Pacific Northwest Region 1995 JA* fSouth Fork Coquille Wate1hed Analysis Iteration 1.0 Powers Ranger Distric, Slsklyou National Forest September 1995 SOUTHERN OREGON UNWVERSiTY LIBRARY ASHLAND, OREGON 97520 United Stat. Depaenent of Agnculure Forest Service Pacific Northwest Region 1995 SOUTH FORK COQUILLE WATERSHED ANALYSIS ITERATION 1.0 I have read this analysis and it meets the Standards and Guidelines for watershed analysis required by an amendment to the Forest Plan (Record of Decision dated April 1994). Any additional evidence needed to make a decision will be gathered site-specifically as part of a NEPA document or as an update to this document. SIGNED CoQ 4 DATE q 1T2 letE District Ranger Powers Ranger District Siskiyou National Forest South Fork Coquille Watershed Analysis - September 1995 Developed by Interdisciplinary Team Members: Steve Harbert Team leader Betsy Howell Wildlife Biologist Dave Shea Botantist, Wildlife Biologist Ruth Sisko Forester Cindy Ricks Geologist Chris Parks Hydrologist Max Yager Fish Biologist Kathy Helm Writer-Editor (March-April 1995), BLM Tina Harbert Writer-Editor (May-July 1995), Powers R.D. Joe Hallett Cultural Resource Key Support: Joel King Forest Planner, Siskiyou National Forest Sue Olson Acting District Ranger, Powers R.D. (Jan-May 1995) Carl Linderman District Ranger, Powers R.D. Marshall Foster GIS, Powers R.D. Jodi Shorb Computer Assistant Linda Spencer Computer Support For Further Information, contact: Powers Ranger District Powers, OR 97466 (503) 439-3011 The policy of the United States Department of Agriculture Forest Service prohibits discrimination on the basis of race, color, national origin, age, religion, sex, or disability, familial status, or political affiliation.
    [Show full text]
  • RV Sites in the United States Location Map 110-Mile Park Map 35 Mile
    RV sites in the United States This GPS POI file is available here: https://poidirectory.com/poifiles/united_states/accommodation/RV_MH-US.html Location Map 110-Mile Park Map 35 Mile Camp Map 370 Lakeside Park Map 5 Star RV Map 566 Piney Creek Horse Camp Map 7 Oaks RV Park Map 8th and Bridge RV Map A AAA RV Map A and A Mesa Verde RV Map A H Hogue Map A H Stephens Historic Park Map A J Jolly County Park Map A Mountain Top RV Map A-Bar-A RV/CG Map A. W. Jack Morgan County Par Map A.W. Marion State Park Map Abbeville RV Park Map Abbott Map Abbott Creek (Abbott Butte) Map Abilene State Park Map Abita Springs RV Resort (Oce Map Abram Rutt City Park Map Acadia National Parks Map Acadiana Park Map Ace RV Park Map Ackerman Map Ackley Creek Co Park Map Ackley Lake State Park Map Acorn East Map Acorn Valley Map Acorn West Map Ada Lake Map Adam County Fairgrounds Map Adams City CG Map Adams County Regional Park Map Adams Fork Map Page 1 Location Map Adams Grove Map Adelaide Map Adirondack Gateway Campgroun Map Admiralty RV and Resort Map Adolph Thomae Jr. County Par Map Adrian City CG Map Aerie Crag Map Aeroplane Mesa Map Afton Canyon Map Afton Landing Map Agate Beach Map Agnew Meadows Map Agricenter RV Park Map Agua Caliente County Park Map Agua Piedra Map Aguirre Spring Map Ahart Map Ahtanum State Forest Map Aiken State Park Map Aikens Creek West Map Ainsworth State Park Map Airplane Flat Map Airport Flat Map Airport Lake Park Map Airport Park Map Aitkin Co Campground Map Ajax Country Livin' I-49 RV Map Ajo Arena Map Ajo Community Golf Course Map
    [Show full text]
  • USGS Professional Paper 1740
    Age, Stratigraphy, and Correlations of the Late Neogene Purisima Formation, Central California Coast Ranges By Charles L. Powell II1, John A. Barron1, Andrei M. Sarna-Wojcicki1, Joseph C. Clark2, Frank A. Perry3, Earl E. Brabb4, and Robert J. Fleck1 Abstract Counties inland to the San Andreas Fault (fig. 1). These scat- tered outcrops have been grouped as the Purisima Formation The Purisima Formation is an important upper Miocene because they are all fine- to coarse-grained clastic rocks, with and Pliocene stratigraphic unit in central California, cropping dark andesitic fragments and locally abundant silicic tephra, out from the coast at Point Reyes north of San Francisco to and occupy the same stratigraphic position at their various more extensive exposures in the Santa Cruz Mountains to the exposures. Since first described by Haehl and Arnold (1904), south. The fine-grained rocks in the lower parts of the Puri- the Purisima Formation has been considered to be of Pliocene sima Formation record a latest Miocene transgressive event, or of late Miocene to Pliocene age. Differing age assignments whereas the middle and upper parts of the formation consist have resulted from the wide stratigraphic range of many com- of increasingly clastic-rich siltstones and sandstones resulting monly encountered megafossils and from the lack of agree- from uplift of adjacent coastal regions and the Sierra Nevada ment on the placement of the Miocene-Pliocene Series bound- during Pliocene transgressive and regressive sea-level events. ary between the provincial megafaunal chronology and that Exposures of the Purisima occur in three different, fault- of international usage.
    [Show full text]